The present invention relates to a heating device for footwear, particularly for ski boots.
Various heating devices are currently known, applicable to footwear in general and usually consituted by an insole insertable within the upper and provided, either internally or on one of its surfaces, with an electric resistor connectable to a power source.
The power source is usually placed externally to the boot, since it is bulky and requires switches accessible to the user for the delivery of power at the required moment.
It is thus known to use as power source a battery of accumulators arrangeable externally to the boot.
It is also known to locate the electric resistor at a sock which can be worn by the skier.
All said known types of devices have, however, some disadvantages; in case of stress, in fact, the accumulators may detach from their support, severing the wires.
Furthermore, the wires are located externally to the boot, and may get accidentally caught and thus be cut.
As a partial solution to these disadvantages, a boot has been disclosed in which the accumulators are arranged within a suitable cavity provided within the heel and power a resistor located within an inner sole.
This type of device, however, also has some disadvantages: it is in fact necessary to provide a particular structure for the inner shoe, the power source and the resistor being furthemore difficult to access for any maintenance.
A partial solution to these disadvantages is disclosed in U.S. Pat. No. 4,507,877, filed Jan. 10, 1983 by this applicant, in which a heating device comprises an electric resistor located on the inner shoe of a ski boot, at the foot of the user, and electrically connected to at least one electric accumulator accommodated in a seat defined in said inner shoe.
This heating device is not free from disadvantages: it is in fact necessary to provide an inner shoe of a particular type, downwardly provided with a rigid foot resting surface, requiring therefor the provision of a complementarily shaped seat at the wedge of the shell.
The particular structure of the inner shoe, furthermore, does not allow its interchangeability within the various models of a line of boots.
Another disadvantage resides in the fact that if it is necessary to check the operation of the various electric components it is impossible for the skier to use the boot, since the inner shoe must be removed.
Ski boots are also known having, at the rear and/or front quarter, a suitable seat for a removable battery of accumulators.
However, even this type of solution has the disadvantage of having to design the front or rear quarter of the boot with a special structure adapted to accommodate said container, thus increasing production costs and furthermore requiring more stringent testing, once the boot is assembled, to verify the correct operation of the components.
U.S. Pat. No. 3,906,185, discloses an insole provided with an electric resistor and adapted to be fitted into a shoe or boot. The resistor is powered by a power pack containing rechargeble batteries and adapted to be carried by the user, for example at the belt.
Although the heated insole is easily adaptable to different shoe sizes, the external battery pack is clearly an inconvenience especially for sports use.